Modelling in port development

Planning and design

When a developer or a public body makes a multi-million dollar investment in a new port or terminal, or an extension to an existing facility, it needs firm assurances that the asset created will be fit for purpose. As well as ensuring that the infrastructure will be operationally robust, the fitness for purpose test also covers the need to withstand the forces of nature throughout its planned life.

Do not assume…calculate
Historically this was done using experience and judgment as well as by adopting safety margins based on historical records often consisting of short-term observations and anecdotal data for episodic storm events. With improved measurements, satellite observations and mathematical models, the rule today is “do not assume…calculate”. Thus, modern tools allow us to predict the future conditions that the planned set of structures will need to withstand with greater certainty, resulting in safe and economical design, such that structures are neither over nor under designed. Computer based mathematical models and simulations provide designers with the opportunity to use comprehensive data-sets and run multiple scenarios quickly and cost-effectively to assess how design variations will influence the effectiveness and fitness for purpose of the overall design. With many excellent modelling tools available on the market, the added value for the client lies in how knowledge and experience are applied to ensure that simulation and modelling produces robust, repeatable outputs.

Following the creation of the first outline design, the analysis process involves testing the layouts and design variations created against simulated environmental conditions that are likely to occur over the design life of the various components of the facility. These could range from the routine conditions that

could be met on a continual “ambient” basis to extreme events that could have a very low statistical probability. Whilst the ambient climate is typically used for determining operational conditions, the extreme event climate is used for design of infrastructure. Usually a number of options for layouts and designs are tested to determine the most suitable arrangement.

Using the correct data in the model
In order to model any particular scenario accurately, a wide range of parameters needs to be identified and quantified. This can include waves, currents, flow circulation, siltation, storm surges, shoreline changes, effect of waves on breakwaters and sea defences, navigation for different sizes and types of ships and mooring forces and stresses generated from them. The reliability of the models is determined by rigorous model calibration, comparing field measurements with the model predictions. In addition to gathering secondary data sources from local research or regulatory agencies, extensive field measurements are utilised whilst planning the model studies so that the models are sound representations of the natural environment.

A successful simulation and modelling programme will not only provide loadings for civil and structural design but will also provide an insight into potential operational and commercial issues. These might include:

Are all-weather operations possible and if not, what is the downtime? Will the extreme climate greatly increase project costs? What are the likely operational costs due to maintenance dredging? Are there any limitations to operating and handling different cargo or vessels at the port? What is the likelihood of environmental impacts due to pollutant release, oil spill, shoreline erosion and loss of critical habitats?

It’s not just about the computer.....
The advent of computer-based simulation and modelling has given the designer the ability to manipulate data in a way that would have been unthought of just twenty years ago. However the old IT adage ‘GIGO’ - Garbage In, Garbage Out still holds true. Without the knowledge and experience to select suitable input data and interpret the outputs correctly, simulation and modelling will not deliver the added value that they should.

Global wave hindcast models have been developed by a number of agencies, including BMT, to provide estimates of the past 20+ years of offshore wave climate. BMT uses SWAN to transform the offshore wave climate to nearshore areas and also uses BOUSS2D to estimate tranquility in sheltered harbours, when diffraction and reflection are important processes in estimation of wave climate. SWAN is also used to estimate storm related waves due to tropical cyclones.

Suren Vakil

Suren Vakil (Managing Director of BMT Consultants India) is a Chartered Engineer and Environmental Manager. With 25 years’ experience in consultancy including 13 years in the UK and 12 years in India, he has been involved in projects located across Europe, the Middle East and the Indian subcontinent. Suren has wide experience of marine as well as infrastructure projects, holding Project Director roles for projects at Chennai Container Terminal, Gujarat Pipavav Port, Mundra Port including proposed new ports at Kulpi, Simar, Vizhinjam, Dahej, Khambhat, Gojiness and Karaikal amongst others.